cell communication and signal transduction, homeostasis and feedback

Question 1

direct contact

Answer 1

communication through cell junctions

signaling substances and other material dissolved in the cytoplasm can pass freely between adjacent cells

Question 2

animal cells direct contact

Answer 2

gap junctions

Question 3

plant cells direct contact

Answer 3

plasmodesmata

Question 4

direct contact example

Answer 4

immune cells

antigen presenting cells (APCs) communicate to T cells through direct contact

Question 5

local regulators

Answer 5

a secreting cell will release chemical messages (local regulators/ligands) that travel a short distance through extra cellular fluid

chemical messages will cause a response in a target cell

Question 6

local regulators examples

Answer 6

paracrine signaling

synaptic signaling

Question 7

paracrine signaling

Answer 7

secretory cells release local regulators (ie growth factors) via exocytosis to an adjacent cell

Question 8

synaptic signaling

Answer 8

occurs in animal nervous systems

neurons secrete neurotransmitters and they diffuse across the synaptic cleft (space between the cell and target cell)

(can be considered long distance signaling depending on the length of the neuron)

Question 9

long distance signaling

Answer 9

animals and plants use hormones for long distance signaling

Question 10

long distance signaling in plants

Answer 10

plants release hormones that travel in the plant vascular tissue (xylem and phloem) or through the air to reach target tissues

Question 11

long distance signaling in animals

Answer 11

animals use endocrine signaling by which specialized cells release hormones into the circulatory system where they reach target cells

Question 12

long distance signaling example

Answer 12

insulin

insulin is released by the pancreas into the bloodstream where it circulated through the body and binds to target cells

Question 13

three stages of cell-to-cell messages

Answer 13

1- reception
ligand binds to receptor

2- transduction
signal is converted

3- response
a cell process is altered

Question 14

reception

Answer 14

the detection and receiving of a ligand by a receptor in the target cell

Question 15

receptor

Answer 15

macromolecule that binds to a signal molecule (ligand)

all receptors have an area that interacts with the ligand and an area that transmits a signal to another protein

Question 16

what happens when the ligand binds to the receptor?

Answer 16

allows the receptor to interact with other cellular molecules and initiated transduction signal

Question 17

plasma membrane receptors bind to ligands that are

Answer 17

polar, water-soluble

large

Question 18

plasma membrane receptors examples

Answer 18

G protein coupled receptors (GPCRs)

ligand-gated ion channels

Question 19

where are intracellular receptors found?

Answer 19

the cytoplasm or nucleus of target cells

Question 20

intracellualr receptors bind to ligands that

Answer 20

can pass through the plasma membrane (ie hydrophobic molecules)

steroid and thyroid hormones
gases like nitric oxide

Question 21

transduction

Answer 21

the conversion of an extra cellular signal to an intracellular signal that will bring about a cellular response

requires a sequence of changes in a series of molecules known as a signal transduction pathway

Question 22

signal transduction pathway regulates protein activity through

Answer 22

phosphorylation by the enzyme protein kinase, which relays signal inside cell

dephosphorylization by the enzyme phosphatase, which shuts off pathways

Question 23

second messengers

Answer 23

small, non-protein molecules and ions that help relay the message and amplify the response during transduction

Question 24

common second messenger

Answer 24

cAMP (cyclic AMP)

Question 25

response

Answer 25

the final molecule in the signaling pathway converts the signal to a response that will alter a cellular response

Question 26

mutations to receptor proteins or to any component of the signaling pathway will result in a change to the blank of the signal

Answer 26

transduction

Question 27

two important categories of cell membrane receptors in eukaryotic organism

Answer 27

G protein coupled receptors (GPCRs)

ion channels

Question 28

GPCRs

Answer 28

important in animal sensory systems

bind to a G protein that can bind to a GTP (similar to ATP)

GPCR and G protein are inactive until ligand binding to GPCR on the extra cellular side

ligand binding causes cytoplasmic side to change shape and allows for the G protein to bind to GPCR (GPCR and G protein activate and GDP becomes GTP)

part of activated G protein can then bind to enzyme and activate it, amplifying signal and leads to a cellular response

Question 29

ligand ion channels

Answer 29

located in plasma membrane

important in nervous system

when a ligand binds to the receptor, the “gate” opens or closes to allow diffusion of specific ions

Question 30

set points

Answer 30

values for physiological conditions that the body tries to maintain

have a normal range for which it can fluctuate

Question 31

homeostasis

Answer 31

state of relatively stable internal conditions

Question 32

body maintains homeostasis through

Answer 32

feedback loops

Question 33

two types of feedback loops

Answer 33

positive and negative

Question 34

stimulus

Answer 34

variable that will cause a response

Question 35

receptor/sensor

Answer 35

sensory organs that detect a stimulus; this information is sent to the control center (brain)

Question 36

effector

Answer 36

muscle or gland that will respond

Question 37

response

Answer 37

changes (decreases or increases) the effect of the stimulus

Question 38

negative feedback

Answer 38

reduces the effect of a stimulus

Question 39

negative feedback examples

Answer 39

sweat
blood sugar
breathing rate

Question 40

positive feedback

Answer 40

increases the effect of a stimulus

Question 41

positive feedback examples

Answer 41

child labor
blood clotting
fruit ripening

Question 42

disease

Answer 42

when the body is unable to maintain homeostasis

Question 43

cell signaling as a means of homeostasis

Answer 43

in order to maintain homeostasis, the cells in a multicellular organism must be able to communicate

communication occurs through signal transduction pathways